Plant detection systems comprising a photodetector housing with a detector lens and an aperture plate

Abstract

A plant detection system includes a radiation module and a photodetector system. The photodetector system includes a photodetector housing, one or more photodetectors, a detector lens, and an aperture plate. The aperture plate is disposed within the photodetector housing between the detector lens and the one or more photodetectors and has an aperture extending therethrough. The detector lens and the aperture plate are configured so that stray radiation received by the detector lens is directed through the aperture in the aperture plate or onto a surface of the aperture plate without being directed onto sidewalls of the photodetector housing.

What is claimed is: 
     
       1. A plant detection system, comprising:
 a radiation module configured to emit a beam comprising radiation at a first wavelength and radiation at a second wavelength different from the first wavelength, the radiation at the first wavelength modulated with a first signal having a first phase, and the radiation at the second wavelength modulated with a second signal having a second phase different from the first phase; and 
 a photodetector system comprising:
 a photodetector housing having sidewalls forming a cylindrical shape therebetween; 
 one or more photodetectors disposed within the photodetector housing, the one or more photodetectors configured to receive reflected portions of the beam and generate an electrical signal based on the reflected portions of the beam; 
 a detector lens configured to direct the reflected portions of the beam onto at least one of the one or more photodetectors; and 
 an aperture plate disposed within the photodetector housing between the detector lens and the one or more photodetectors, the aperture plate being free of plastic on a surface facing the detector lens and having an aperture extending through a center portion of the aperture plate, the surface of the aperture plate facing the detector lens extending between the sidewalls of the photodetector housing so that at least some outer edges of the aperture plate are adjacent to the sidewalls of the photodetector housing. 
 
 
     
     
       2. The system of  claim 1  wherein at least some of the outer edges of the aperture plate abut the sidewalls of the photodetector housing. 
     
     
       3. The system of  claim 1  wherein the aperture plate is coupled to the sidewalls of the photodetector housing. 
     
     
       4. The system of  claim 1  wherein a portion of the aperture plate extends orthogonal to the sidewalls of the photodetector housing and a portion of the aperture plate extends parallel to the sidewalls of the photodetector housing. 
     
     
       5. The system of  claim 1  wherein the photodetector housing includes one or more ledges extending inward from the sidewalls, and the aperture plate is coupled to the one or more ledges. 
     
     
       6. The system of  claim 1  wherein the one or more photodetectors and the aperture plate are coupled to a substrate. 
     
     
       7. The system of  claim 1  wherein the surface of the aperture plate facing the detector lens comprises metal. 
     
     
       8. The system of  claim 1  wherein the photodetector housing comprises plastic and the aperture plate comprises metal. 
     
     
       9. The system of  claim 1  wherein edges of the aperture form a polygon shape in the aperture plate. 
     
     
       10. A plant detection system, comprising:
 a radiation module configured to emit a beam of radiation; and 
 a photodetector system comprising:
 a photodetector housing having sidewalls forming a cylindrical shape therebetween; 
 one or more photodetectors disposed near a first end of the cylindrical shape, the one or more photodetectors configured to receive reflected portions of the beam of radiation and generate an electrical signal based on the received portions of the beam of radiation; 
 a detector lens disposed near a second end of the cylindrical shape opposite the first end, the detector lens configured to direct the reflected portions of the beam onto at least one of the one or more photodetectors; and 
 an aperture plate disposed within the photodetector housing between the detector lens and the one or more photodetectors and having an aperture extending therethrough, a surface of the aperture plate facing the detector lens extending between the sidewalls of the photodetector housing so that at least some outer edges of the aperture plate are adjacent to the sidewalls of the photodetector housing. 
 
 
     
     
       11. The system of  claim 10  wherein at least some of the outer edges of the aperture plate abut the sidewalls of the photodetector housing. 
     
     
       12. The system of  claim 10  wherein the aperture plate is coupled to the sidewalls of the photodetector housing. 
     
     
       13. The system of  claim 10  wherein a portion of the aperture plate extends orthogonal to the sidewalls of the photodetector housing and a portion of the aperture plate extends parallel to the sidewalls of the photodetector housing. 
     
     
       14. The system of  claim 10  wherein the photodetector housing includes one or more ledges extending inward from the sidewalls, and the aperture plate is coupled to the one or more ledges. 
     
     
       15. The system of  claim 10  wherein the one or more photodetectors and the aperture plate are coupled to a common surface. 
     
     
       16. The system of  claim 10  wherein the surface of the aperture plate facing the detector lens comprises metal. 
     
     
       17. A plant detection system, comprising:
 a radiation module configured to emit a beam of radiation; and 
 a photodetector system comprising:
 a photodetector housing having sidewalls extending between a first end of a housing and a second end of the housing; 
 one or more photodetectors disposed near a first end of the housing, the one or more photodetectors configured to receive reflected portions of the beam of radiation and generate an electrical signal based on the received portions of the beam of radiation; 
 a detector lens disposed near a second end of the housing opposite the first end, the detector lens configured to direct the reflected portions of the beam onto at least one of the one or more photodetectors; and 
 an aperture plate disposed within the photodetector housing between the detector lens and the one or more photodetectors and having an aperture extending therethrough, the detector lens and the aperture plate configured so that stray radiation received by the detector lens is directed through the aperture in the aperture plate or onto a surface of the aperture plate without being directed onto the sidewalls of the photodetector housing. 
 
 
     
     
       18. The system of  claim 17  wherein at least some outer edges of the aperture plate abut the sidewalls of the photodetector housing. 
     
     
       19. The system of  claim 17  wherein the aperture plate is coupled to the sidewalls of the photodetector housing. 
     
     
       20. The system of  claim 17  wherein the aperture plate is shaped to prevent the stray radiation focused by the detector lens from impinging directly on the sidewalls of the photodetector housing.